This invention relates to tufting machine gauge parts, and more particularly to a modular hook assembly for staggered needle cut pile tufting machines.
In the production of tufted pile fabric each reciprocating needle cooperates with a loop or hook which seizes a loop of yarn from the needle and releases the loop to form loop pile fabric or holds the loop until it is cut by a knife acting in scissors-like fashion against the side of the hook to form cut pile fabric. The gauge of the pile fabric is determined by the spacing between adjacent gauge parts, i.e. the needles, hooks and knives, of the tufting machine. To produce fine gauge pile fabric, i.e. one tenth gauge and smaller, the spacing between adjacent gauge parts is 0.1 inch and smaller. As a consequence of the close spacing between the adjacent gauge part in fine gauge tufting machines, great difficulty has been experienced in providing hooks at the required spacing and maintaining the spacing. Moreover, in cut pile machines the transverse pressure applied to the individual hooks by the respective knives can give rise to deflection of the tips of the hooks. In view of the high accuracy required when the gauge parts are closely spaced it is highly desirable, if not mandatory, that this deflection be minimized to insure accurate and consistent seizing of the yarn hook from the cooperating needle. The conventional mounting of the hooks in corresponding slots in the hook bar and their securement by set screws creates difficulties in aligning closely spaced hooks and minimizing the deflections thereof. Furthermore, in the event of damage to a series of hooks or when such hooks are worn, the replacement of a new set is particularly demanding of time.
To overcome these problems it has been proposed to provide a hook module wherein the respective hook shanks are imbedded in a common body member in side-by-side disposition. Such constructions are illustrated in United Kingdom design registration Nos. 980,060 and 980,062. Such construction substantially eliminates the difficulties of aligning the hooks in the hook bar of the tufting machine since the hooks are aligned in a jig during the formation of the module and each body member may have an alignment surface for clamping of the module to a hook bar in the tufting machine.
Moreover, in fine gauge tufting machines it is known to locate the needles in staggered relationship in two rows and to mount cooperating hooks in a slotted hook bar, the hooks cooperating with the needles in one row having a longer bill than the hooks cooperating with the needles of the other row. For purposes of aligning the hooks in the hook bar, the throats of both the long billed set of hooks and the short bill set of hooks may be in alignment in the longitudinal direction of the hook bar, as illustrated in U.S. Pat. Nos. 4.003,321 and 3,913, 505. This, however, is unnecessary when hook modules are utilized. There does exist however the difficulty that in the event of damage to one hook in a module the entire module must be replaced, and similarly if knife pressure on one or the other sets of hooks is greater than on the other that set would have to be reground or replaced more frequently than the other set of hooks.